Field of the Invention
The present invention relates to printing apparatuses enabling two-sided printing and, in particular, relates to a printing apparatus performing a two-sided printing process at high speed, a control method therefore, and a storage medium storing a control program therefor.
Description of the Related Art
When performing two-sided printing using a plurality of sheets, a printing apparatus sequentially obtains a print data corresponding to each page from a first page, generates image processing data by performing an image process on the obtained print data, and prints the image processing data on front and back sides of each sheet. There is known two-sided printing (hereinafter referred to as “normal two-sided printing”) by which a print data corresponding to each page is printed on back and front side of each sheet in the order of page 2, page 1, page 4, page 3, page 6, and page 5. Moreover, there is also known two-sided printing (hereinafter referred to as “high-speed two-sided printing”) by which a print data corresponding to each page is printed in the order of page 2, page 4, page 1, page 6, page 3, and page 5 in order to shorten printing waiting time resulting from conveyance of sheets in printing (for example, see Japanese Laid-Open Patent Publication (Kokai) No. 2002-337417 (JP 2002-337417A)).
Basically, printing on each sheet is started after image processing data that will be printed on a sheet is generated. However, in the high-speed two-sided printing, since priority is given to improvement in efficiency of the conveyance of each sheet and each sheet is conveyed regardless of an order of obtaining print data, an image processing data corresponding to a certain sheet may not be generated by the time when printing on the certain sheet is started. In this case, a printing-process error occurs and a sheet in printing stays in the printing apparatus, for example. That is, in the high-speed two-sided printing, when an image processing data corresponding to a sheet is not generated at the start time of printing on the sheet concerned, the printing process enters into a suspended state (for example, see Japanese Laid-Open Patent Publication (Kokai) No. 2010-173186 (JP 2010-173186A)).
Accordingly, the technique of JP 2010-173186A deteriorates efficiency of the printing process when generation of the image processing data takes time.